query 2 wordpress database tables at once - wordpress

Question

I have the following query which i am running:
$query = "SELECT post_title, ID, post_date_gmt, post_author
FROM wp_posts
WHERE post_type='course-manager'
AND post_status='publish'
AND SUBSTRING(post_date_gmt,1,4) = '$this->yearGet'
AND SUBSTRING(post_date_gmt,6,2) = '$this->monthGet'
AND post_author = '$userid'
ORDER BY post_title";
$query_result = mysql_query ($query);
while ($info = mysql_fetch_array($query_result))
{
currently this is querying just the wordpress posts table. i would like to also query data from the wordpress postmeta table, an example would be like this where i have added the "AND course_date which is within the postmeta table:
$query = "SELECT post_title, ID, post_date_gmt, post_author
FROM wp_posts
WHERE post_type='course-manager'
AND post_status='publish'
AND SUBSTRING(post_date_gmt,1,4) = '$this->yearGet'
AND SUBSTRING(post_date_gmt,6,2) = '$this->monthGet'
AND post_author = '$userid'
AND course_date = '$this->yearGet'
ORDER BY post_title";
$query_result = mysql_query ($query);
while ($info = mysql_fetch_array($query_result))
{
any help would be greatly appreciated

Answer 1

If you need to query a combined set of data whose source is from more than one table, you need to do a join. Basically, you need to make the connection between the 2 tables, in the post and postmeta case, that connection would be the post id. So the query should look like this:
SELECT a.something, b.anotherthing
FROM wp_posts AS a JOIN wp_postmeta AS b
ON a.ID = b.post_id
//followed by all of your where clause...